The present invention relates to a dielectric filter device having a stripline filter and dielectric blocks.
FIG. 1 discloses a dielectric filter device in a prior art wherein it comprises a plurality of juxtaposed dielectric coaxial resonators each of which includes a rectangular parallelepiped dielectric block A. Each dielectric block A is provided with a groove B having circular cross section and extended in the center axial direction, and an external conductive layer C on an outer surface except a front surface thereof. The groove B in each dielectric block A has the inner surface coated with a conductive layer D. An example of such a filter arrangement is disclosed in Japanese Patent Kokai No. 3-136502.
Such a conventional filter arrangement has a disadvantage in that it is larger in height because each of the juxtaposed dielectric coaxial resonators comprises the rectangular parallelepiped dielectric block. Therefore, it does not substantially meet a requirement for a size reduction of potable communication equipments such as potable telephones incorporating such a filter device.
On the other hand, as a filter device for use with such potable communication equipments there is also known a stripline filter in which resonator conductors are arranged on a dielectric substrate. The stripline filter permits a reduction in thickness but shows a low Q value and thus a large insertion loss is to be involved.